Stratigraphy is the branch of geology that studies rock layers (strata) and arranges them in the order in which they were formed. A stratigraphic succession is that ordered sequence — oldest at the bottom, youngest at the top — grouped into units such as supergroups, groups and formations, and placed against the geological time scale. Because many of Odisha’s rocks are very old and have been folded, metamorphosed and intruded by granites many times, its succession is worked out not only from superposition but also from cross-cutting relationships, metamorphic grade and, increasingly, radiometric (U–Pb zircon) dating.
Odisha has one of the longest geological records in India. Its rocks span more than 3.5 billion years, from some of the oldest crust on Earth in the Singhbhum (North Odisha) Craton to the deltaic and coastal sands still being laid down by the Mahanadi, Brahmani and Baitarani. According to the Directorate of Geology, Odisha:
- about 72.5% of the state is made of Precambrian metamorphic and igneous rocks of Archaean and Proterozoic age;
- about 8% is covered by the coal-bearing Gondwana Supergroup (Permian to Cretaceous);
- the remaining area is occupied by Tertiary and Quaternary formations — laterite, coastal and deltaic alluvium, sand dunes and river sediments.
The succession can be read as four great chapters:
- Archaean cratonic nuclei — the Singhbhum Craton in the north and the Bastar Craton in the west, with their gneisses, granites and greenstone-type Iron Ore Group belts.
- Proterozoic mobile belts and basins — the Eastern Ghats Granulite Belt, the Singhbhum and Gangpur fold belts, and the platform sediments of the Chhattisgarh–Khariar–Pairi basins.
- Gondwana rift basins — the Talcher and Ib River coalfields and the Athgarh basin.
- Cenozoic cover — the Miocene Baripada beds, laterites, and the Quaternary alluvium of the coastal plains.
Generalised Stratigraphic Succession of Odisha
The table lists the main units from youngest (top) to oldest (bottom). Ages for the Precambrian units are approximate and based on published radiometric dates; different authors group some units differently.
| Era / Period | Approximate age | Stratigraphic unit | Main rock types | Main areas in Odisha |
|---|---|---|---|---|
| Quaternary (Holocene–Pleistocene) | < 2.6 Ma | Coastal and deltaic alluvium, beach sands, dunes, older alluvium | Sand, silt, clay, gravel; heavy-mineral beach sands | Mahanadi–Brahmani–Baitarani delta, Subarnarekha plain, Chilika, Ganjam coast |
| Tertiary–Quaternary | Late Tertiary onward | Laterite and lateritic gravel (high- and low-level) | Laterite, bauxite cappings | Khordha, Bhubaneswar, Cuttack uplands; Eastern Ghats plateaus (bauxite) |
| Tertiary (Miocene) | c. 23–5 Ma | Baripada beds | Fossiliferous clay, limestone, sandstone | Mayurbhanj (Baripada, Mukurmatia) |
| Upper Gondwana (Jurassic–Early Cretaceous) | c. 200–100 Ma | Athgarh Formation | Sandstone, shale, conglomerate (plant fossils) | Athgarh basin, Cuttack–Khordha |
| Lower Gondwana (Permian–Triassic) | c. 300–200 Ma | Kamthi, Barren Measures, Barakar, Karharbari, Talcher formations | Sandstone, shale, coal, tillite, boulder beds | Talcher and Ib River coalfields (Angul, Jharsuguda, Sundargarh, Sambalpur) |
| Late Proterozoic (Neoproterozoic) | c. 1.0–0.6 Ga | Chhattisgarh Supergroup (incl. Khariar and Pairi groups) | Sandstone, shale, limestone, dolomite | Bargarh, Nuapada, Kalahandi, Balangir border |
| Proterozoic (Meso–Neoproterozoic) | c. 1.6–0.5 Ga (main metamorphism c. 1.0–0.95 Ga) | Eastern Ghats Supergroup | Khondalite, charnockite, leptynite, migmatite, anorthosite, alkaline rocks | Koraput, Rayagada, Kalahandi, Kandhamal, Ganjam, Gajapati, Nayagarh, Balangir, Angul |
| Palaeo–Mesoproterozoic | c. 2.2–1.6 Ga | Gangpur Group; Singhbhum Group (Chaibasa) with Dalma volcanics; Kolhan Group; Newer Dolerite dykes | Phyllite, schist, quartzite, limestone/dolomite, manganese horizons; volcanics; dolerite | Sundargarh (Gangpur), Mayurbhanj–Keonjhar border, Kolhan basin |
| Late Archaean–Palaeoproterozoic | c. 2.8–2.2 Ga | Dhanjori and Simlipal volcano-sedimentary groups | Basalts, quartzite, conglomerate | Simlipal (Mayurbhanj), Dhanjori basin |
| Archaean | c. 3.1–3.0 Ga | Mayurbhanj Granite, Bonai Granite and younger granites | Granite, granophyre | Mayurbhanj, Bonai (Sundargarh), Keonjhar |
| Archaean | c. 3.5–3.0 Ga | Iron Ore Group (Iron Ore Supergroup / Badampahar Group) | Banded iron formation (BIF), shale, ultramafics, volcanics | Keonjhar, Sundargarh (Bonai), Mayurbhanj (Gorumahisani–Badampahar) |
| Archaean | c. 3.4–3.1 Ga | Singhbhum Granite Complex | Granite, granodiorite, tonalite | Keonjhar, Mayurbhanj |
| Archaean | c. 3.45 Ga | Older Metamorphic Tonalite Gneiss (OMTG) | Tonalite–trondhjemite gneiss | Champua–Keonjhar area |
| Archaean (oldest) | c. 3.5–3.3 Ga (zircons to c. 4.2 Ga) | Older Metamorphic Group (OMG) | Pelitic schists, quartzites, para-amphibolites | Champua and Onkadelli area, Keonjhar |
| Archaean (west) | c. 3.5–2.5 Ga | Bastar Craton basement | Granite gneiss, migmatite, granite | Nuapada, Bargarh, Balangir, Kalahandi (west) |
Geological Column of Odisha at a Glance
The column shows how the state’s mineral wealth is tied to its stratigraphy: iron ore and chromite to the Archaean cratons, manganese and carbonate rocks to the Proterozoic fold belts, bauxite to the laterite capping of the Eastern Ghats, coal to the Gondwana basins, and beach-sand minerals and groundwater to the youngest coastal deposits.
The Archaean Basement
1. Singhbhum (North Odisha) Craton
The Singhbhum Craton — called the Singhbhum–North Odisha Craton or North Odisha Iron Ore Craton in Odisha — covers Keonjhar, Mayurbhanj and parts of Sundargarh and Jajpur, extending north into Jharkhand. It is one of the oldest pieces of continental crust in India. Its classic succession (after Saha, 1994, with later radiometric revisions), from oldest to youngest, is:
| Unit | Approximate age | Description |
|---|---|---|
| Older Metamorphic Group (OMG) | c. 3.5–3.3 Ga; detrital zircons to c. 4.2 Ga | The oldest rocks of the craton: pelitic schists, quartz-sericite schists, quartzites and para-amphibolites, exposed as enclaves around Champua and Onkadelli in Keonjhar. Zircons from these rocks are among the oldest found in India. |
| Older Metamorphic Tonalite Gneiss (OMTG) | c. 3.45–3.35 Ga | Tonalite–trondhjemite–granodiorite (TTG) gneisses that intruded the OMG; the first true granitic crust of the region. |
| Singhbhum Granite Complex | c. 3.35–3.1 Ga | A huge composite batholith of granite, granodiorite and tonalite, emplaced in several phases (Singhbhum Granite I, II and III), forming the core of the craton in Keonjhar and Mayurbhanj. |
| Iron Ore Group (IOG) / Iron Ore Supergroup | c. 3.5–3.0 Ga (age debated) | Greenstone-type supracrustal belts of shale, tuff, mafic lava, ultramafics and thick banded iron formation (BIF), arranged in three belts: the Western IOG (Bonai–Keonjhar horseshoe synclinorium of the Badampahar–Joda–Barbil–Noamundi area), the Southern IOG (Daitari–Tomka, with the Sukinda chromite ultramafics), and the Eastern IOG (Gorumahisani–Badampahar, Mayurbhanj). In Odisha the eastern belt is also called the Badampahar Group. |
| Younger granites — Bonai Granite, Mayurbhanj Granite | c. 3.37 Ga (Bonai); c. 3.1–3.0 Ga (Mayurbhanj) | Granite plutons marking the stabilisation (cratonisation) of the Singhbhum crust; the Mayurbhanj Granite includes granophyres and gabbro-anorthosite. |
The Iron Ore Group hosts nearly all of Odisha’s hematite iron ore (Joda, Barbil, Koira, Daitari, Gandhamardan), the Sukinda chromite (about 95% of India’s chromite reserves) and the Joda–Koira manganese deposits.
2. Bastar Craton (western Odisha)
In the far west — Nuapada, western Bargarh, Balangir and Kalahandi — Odisha includes the eastern margin of the Bastar Craton. It is made of Archaean granite gneisses, migmatites and granites (c. 3.5–2.5 Ga) with enclaves of older supracrustal rocks and pegmatites. This basement is overlain by the Neoproterozoic Chhattisgarh basin sediments and is separated from the Eastern Ghats Belt by a major shear zone.
3. Rengali Province
Between the Singhbhum Craton and the Eastern Ghats lies the Rengali Province (around Rengali, Riamal and Deogarh), an Archaean crustal block of granite gneisses, amphibolites and supracrustal belts, bounded by major shear zones on its northern and southern sides. It is usually interpreted as a reworked southern margin of the Singhbhum Craton that was caught up when the Eastern Ghats Belt collided with it.
The Eastern Ghats Supergroup
The Eastern Ghats Granulite Belt (also called the Eastern Ghats Mobile Belt) is the most extensive rock unit of Odisha. It covers almost the whole of southern and central Odisha — Koraput, Rayagada, Kalahandi, Kandhamal, Gajapati, Ganjam, Nayagarh, Boudh, Balangir and southern Angul — and continues south into Andhra Pradesh. These rocks were formed from older sediments and igneous rocks that were buried deep in the crust and metamorphosed at very high temperatures (granulite facies), mainly during a collision about 1.0–0.95 billion years ago (the Grenvillian event, when India joined the supercontinent Rodinia) with an earlier event at c. 1.6–1.5 Ga.
Main rock types
| Rock | Nature | Where common |
|---|---|---|
| Khondalite | Garnet–sillimanite–graphite gneiss formed from clay-rich sediments; named after the Khond (Kondh) hills of Odisha, its type area | Kandhamal, Koraput, Rayagada, Kalahandi, Ganjam, Puri hills |
| Charnockite | Hypersthene-bearing granulite, often dark and massive | Koraput, Kalahandi, Angul, Nayagarh, Balangir |
| Leptynite (quartzo-feldspathic garnet gneiss) | Light-coloured garnetiferous gneiss interlayered with khondalite | Throughout the belt |
| Calc-granulites and quartzites | Formed from impure limestones and sandstones | Scattered bands |
| Migmatites and granite gneisses | Partially melted rocks and granites | Widespread, especially in the northern part of the belt |
| Anorthosite | Plagioclase-rich intrusions | Chilika Lake area (Balugaon–Rambha), Turkel and other bodies in Balangir |
| Alkaline rocks (nepheline syenite and related rocks) | Intrusive complexes along deep faults near the belt’s western margin | Khariar (Nuapada), Rairakhol, Koraput |
Economic importance
- The khondalites weather under a humid tropical climate into thick laterite and bauxite cappings on plateaus such as Panchpatmali (Koraput, NALCO’s mine), Sijimali, Kodingamali and Baphlimali — making Odisha India’s largest bauxite state.
- Graphite (Titlagarh, Balangir; Kalahandi), gemstones (garnet, sapphire, chrysoberyl in Kalahandi and Balangir), sillimanite and manganese (Koraput–Rayagada belt) are also associated with these rocks.
- The resistant charnockite and khondalite ridges form the high Eastern Ghats hills, including Deomali (1,672 m), Odisha’s highest peak.
Proterozoic Fold Belts and Basins
Singhbhum fold belt and northern basins
After the Singhbhum Craton stabilised, rift basins and fold belts developed around it during the Late Archaean and Proterozoic:
| Unit | Approximate age | Rocks | Area |
|---|---|---|---|
| Dhanjori Group and Simlipal Group | c. 2.8–2.2 Ga | Thick basaltic lavas, quartzite, conglomerate; the Simlipal basin is a near-circular volcano-sedimentary basin forming the Similipal hills | Mayurbhanj (Similipal), Dhanjori basin on the Jharkhand border |
| Singhbhum Group (Chaibasa and Dhalbhum formations) with Dalma volcanics | c. 2.4–1.6 Ga | Mica schists, phyllites, quartzites; Dalma mafic–ultramafic volcanic belt | Northern Mayurbhanj; mostly in Jharkhand along the Singhbhum Shear Zone (copper–uranium belt) |
| Kolhan Group | Late Palaeoproterozoic–Mesoproterozoic | Little-deformed conglomerate, sandstone, limestone and shale in small basins on the craton | Keonjhar–Jharkhand border (Kolhan basin) |
| Gangpur Group | Palaeoproterozoic | Phyllites, mica schists, quartzites, carbonaceous slates, dolomite and limestone, with manganese horizons; folded into the Gangpur synclinorium | Sundargarh (Birmitrapur, Gangpur, Bisra area) |
| Newer Dolerite dykes | Several swarms, c. 2.8–1.1 Ga | Dolerite and gabbro dykes cutting the Singhbhum Granite | Keonjhar, Mayurbhanj |
The Gangpur Group supplies the Birmitrapur dolomite and limestone used by the Rourkela Steel Plant and cement industry.
Western platform basins (Neoproterozoic)
In western Odisha, gently dipping, unmetamorphosed sediments rest on the Bastar basement. They belong to the Chhattisgarh Supergroup and its outliers:
- Chhattisgarh basin — the eastern part of this huge basin enters Bargarh and Nuapada; its lower part is sandstone–conglomerate and its upper part shale and limestone (e.g., the Chandi–Charmuria-type limestones), the base of the cement industry around Bargarh.
- Khariar Group — a plateau of sandstones and shales capping the Khariar uplands of Nuapada.
- Pairi Group — small outlier basins of sandstone, shale and limestone along the Odisha–Chhattisgarh border.
These basins are generally placed in the Meso–Neoproterozoic (c. 1.4–0.6 Ga), with the main limestone-bearing part being Neoproterozoic.
The Gondwana Supergroup
After a long gap (unconformity) of several hundred million years, sediments were deposited in fault-bounded rift basins that opened along the Mahanadi and its tributaries when India was part of the supercontinent Gondwana. These basins form the Mahanadi Gondwana Valley, which includes the Talcher Coalfield (Angul), the Ib River Coalfield (Jharsuguda, Sundargarh, Sambalpur) and the smaller Athgarh basin (Cuttack–Khordha). Together they occupy about 8% of Odisha.
Gondwana succession in Odisha (youngest at top)
| Division | Formation | Approximate age | Rocks and features |
|---|---|---|---|
| Upper Gondwana | Athgarh Formation | Jurassic–Early Cretaceous | Sandstones, shales and conglomerates with plant fossils; building stone of many temples (e.g., in Cuttack and Bhubaneswar) |
| Lower Gondwana | Kamthi Formation | Late Permian–Triassic | Coarse ferruginous sandstones and pebbly beds |
| Barren Measures | Late Permian | Shales and sandstones with thin, poor coal seams | |
| Barakar Formation | Early Permian | Sandstones, shales and the thickest coal seams — the main coal-bearing unit of Talcher and Ib River | |
| Karharbari Formation | Early Permian | Coarse sandstones and conglomerates with good-quality coal seams | |
| Talcher Formation | Latest Carboniferous–Earliest Permian | Glacial tillite / boulder beds, rhythmites, needle shales and green sandstones |
The Talcher Formation — a global type section
The Talcher Formation, first described from the Brahmani valley near Talcher in 1856 by W.T. and H.F. Blanford, gives its name to the basal glacial beds of the Gondwana succession all over India. Its boulder beds and striated pebbles are evidence of the Late Palaeozoic glaciation that covered much of Gondwana about 300 million years ago — one of the key observations behind the theory of continental drift.
Economic significance
The Barakar and Karharbari formations hold Odisha’s huge reserves of non-coking thermal coal. The Talcher Coalfield holds the largest coal reserves of any coalfield in India, and together with the Ib Valley coalfield it makes Odisha India’s leading state for coal reserves and a major producer through Mahanadi Coalfields Limited.
Tertiary and Quaternary Formations
Tertiary: the Baripada beds
Tertiary rocks are rare on land in Odisha. The best known are the Baripada beds of Mayurbhanj — soft clays, sandy limestones and sandstones exposed along the Burhabalang river near Baripada (e.g., at Mukurmatia). They contain marine and brackish-water fossils such as foraminifera, molluscs, shark teeth and fish remains, and are assigned a Miocene age. They show that the sea once spread over the northern coastal margin of Odisha.
Far larger Tertiary sequences lie offshore and beneath the coastal plain in the Mahanadi Basin, a sedimentary basin formed when India separated from Antarctica in the Cretaceous. Thick Cretaceous–Tertiary sediments here are explored for oil and natural gas.
Laterite
Laterite is a residual rock produced by intense tropical weathering, rich in iron and aluminium oxides. Two types are recognised:
- High-level laterite — thick cappings on plateaus of the Eastern Ghats (900–1,400 m), developed over khondalite; where alumina-rich, it forms bauxite (Panchpatmali, Sijimali, Kodingamali, Baphlimali).
- Low-level laterite — covering the dissected uplands behind the coast around Bhubaneswar, Khordha, Cuttack, Jajpur, Balasore and Mayurbhanj. Bhubaneswar itself is built on a lateritic upland, and laterite has been the region’s main building stone for centuries.
Quaternary deposits
The youngest deposits form the Coastal Plains of Odisha:
- Older alluvium — higher, oxidised terraces with kankar along the inland margin of the plain.
- Newer (deltaic) alluvium — sands, silts and clays of the combined Mahanadi–Brahmani–Baitarani delta, one of the largest deltas on India’s east coast, and of the Subarnarekha, Budhabalang and Rushikulya plains.
- Coastal and lagoonal deposits — beach ridges, sand dunes, tidal flats, mangrove swamps (Bhitarkanika) and the sediments of Chilika Lake.
- Beach placer sands — heavy-mineral sands rich in ilmenite, rutile, zircon, monazite, sillimanite and garnet, mined at Chhatrapur (Ganjam) by IREL.
- River alluvium — narrow strips along the Mahanadi, Tel, Brahmani and other rivers inland.
Economic Significance of the Succession
| Stratigraphic unit | Minerals / resources |
|---|---|
| Iron Ore Group (Archaean) | Hematite iron ore (Keonjhar, Sundargarh, Mayurbhanj, Jajpur), manganese (Joda–Koira) |
| Ultramafics of the Southern IOG | Chromite (Sukinda valley), nickel |
| Gangpur Group | Dolomite, limestone (Birmitrapur), manganese |
| Eastern Ghats Supergroup and its laterite | Bauxite, graphite, gemstones, manganese, building stone |
| Chhattisgarh Supergroup | Cement-grade limestone (Bargarh, Nuapada) |
| Gondwana Supergroup | Thermal coal (Talcher, Ib Valley), fireclay, sandstone |
| Mahanadi offshore basin (Cretaceous–Tertiary) | Oil and natural gas (exploration) |
| Quaternary beach sands | Ilmenite, rutile, zircon, monazite, sillimanite, garnet |
| Quaternary alluvium | Groundwater, fertile delta soils |
Conclusion
Odisha’s stratigraphic succession is an unusually complete record of Earth history. At its base lie some of the oldest rocks of the Indian subcontinent in the Singhbhum Craton; above them come the Iron Ore Group, the Proterozoic fold belts and platform basins, and the great granulite terrain of the Eastern Ghats, followed after a long gap by the coal-bearing Gondwana rift basins and finally by laterites and the young deltaic plains of the coast. This layered history explains both the landscape of Odisha — its northern plateaus, Eastern Ghats hills and coastal plains — and its exceptional mineral wealth, which makes it India’s leading state for iron ore, chromite, bauxite and coal.
Quick Facts
| Item | Fact |
|---|---|
| Precambrian rocks | About 72.5% of Odisha |
| Gondwana rocks | About 8% of Odisha |
| Oldest rocks | Older Metamorphic Group (Champua–Onkadelli, Keonjhar), c. 3.5–3.3 Ga |
| Oldest granitic crust | Older Metamorphic Tonalite Gneiss, c. 3.45 Ga |
| Main iron-bearing unit | Iron Ore Group (Iron Ore Supergroup) |
| Largest rock unit | Eastern Ghats Supergroup (khondalite–charnockite) |
| Type area of khondalite | Khond (Kondh) hills of Odisha |
| Type area of Talcher Formation | Brahmani valley near Talcher, Angul |
| Gondwana coalfields | Talcher and Ib Valley |
| Tertiary on land | Baripada beds (Miocene), Mayurbhanj |
| Youngest deposits | Deltaic and coastal alluvium, beach sands |
Sources
- Geology and Mineral Resources of Orissa — Directorate of Geology, Government of Odisha
- Geology and Mineral Resources of Odisha — Odisha Reference Annual 2011
- Compendium of Mineral Resources of Orissa — Government of Odisha
- The Singhbhum Craton stratigraphy — StudyHub
- Generalised chronostratigraphic succession in the Singhbhum–Orissa craton (after Saha et al.) — ResearchGate
- Gondwana Supergroup: Damodar, Satpura, Mahanadi and Godavari basins — OpenGeology
- Saha, A.K. (1994), Crustal Evolution of Singhbhum–North Orissa, Eastern India, Geological Society of India Memoir 27.
- Geological Survey of India, Geology and Mineral Resources of Orissa, Miscellaneous Publication 30.
